Short-range communication capability has become more prominent in a wide variety of mobile digital devices, such as cellular phones, personal digital assistants (PDAs), pagers and other mobile devices. Short-range communication provides the devices with the ability to communicate via RFID, Bluetooth®, infrared or other types of short-range communication dependent upon the type of transceiver module associated with the mobile device. Continuous active operation of short-range communication modules, however, consumes significant amounts of power. Therefore, in a typical mobile device with short-range communication capabilities the device is prone to require a larger power supply and/or more frequent charging of the power supply, as compared to the mobile device that is not equipped to communicate via a short-range communication medium. Both larger power supplies and more frequent power supply charging are not viable alternatives in the mobile environment. Larger power supplies lead to larger mobile devices, which is counter-intuitive to the general mobile concept that “smaller is better” or at least more practical. In the same regard, frequent charging of the mobile device power supply is inconvenient for the user and reduces the lifetime expectancy of the power supply.
For example, a typical low frequency RFID reader runs on a 3 Hz scan cycle; meaning that it is activated, i.e., “wakes up”, once every 330 ms to check for RFID tags in the general vicinity. With current technology, this type of repetitive activation can add up to upwards of 20 percent of the power consumed by the mobile device. However, in the vast majority of instances the wake-up period results in no tags read, i.e., within the range of the RFID reader, so that the power that is consumed is unwarranted.
As such, there is a need in the industry to conserve the power in mobile devices associated with short-range communication modules to permit utilization of conventional power supplies and typical power supply charging schedules for the mobile devices. Various attempts have been made to address power management in mobile devices and particularly those devices that are associated with short-range communication.
One type of power-conserving method has been implemented for RFID short-range communication. The method involves limiting the “reading” of the RFID tag to only a portion of the tag, and if the RFID reader identifies that it has previously read the tag based upon the identification portion, the RFID reader does not read the rest of the tag. While this power-conserving method is helpful, the RFID reader still consumes more power than desired and the method does not address the problem of continual active operation.
In another recently developed power conservation method, an appropriate sensor measures the movement of the mobile device and active read operations continue while the movement of the device is unknown. When the movement of the device is identified, however, one or more of the subunits of the device is changed from an active operation mode to a sleep operation mode, where the sleep operation mode consumes less power than the active operation mode. The device then stays in the sleep operation mode while the movement of the device is known, and then changes back to the active operation mode when the movement of the device becomes unknown. Again, while this power-conserving method is helpful, the device still consumes more power than desired because the device is in an active operation mode anytime the movement is unknown, which amounts to most of the time that the device is in use due to the “mobile” nature of the device.
Thus, there is a need for techniques that permit greater conservation of power in mobile devices associated with a short-range communication so that the mobile device does not need a larger power supply or frequent power supply charging. In this regard, a need exists to develop techniques for keeping the short-range communication module active where there is a high likelihood of short-range communication exchange while keeping the short-range communication module less active when the likelihood of short-range communication is lower in order to keep the power consumption optimized. Additionally, a need exists to develop a power saving technique that automatically activates the short communication module without requiring the user of the device to interact with a user interface.